Measuring the blood pressure information of a measurement subject is extremely important in understanding the health of the measurement subject. In recent years, attempts are being made to measure stress on the heart, hardening of the arteries, and so on by measuring pulse waves of measurement subjects, as opposed to simply measuring the systolic blood pressure value (“maximum blood pressure”, hereinafter) and the diastolic blood pressure value (“minimum blood pressure”, hereinafter), the usefulness of which as a representative index of health management is widely accepted at present. Blood pressure information measurement devices are devices for measuring such blood pressure information, and such devices are expected to have a further role in the early detection, prevention, and treatment of circulatory system conditions. Note that various types of circulatory system information generally fall under the umbrella of “blood pressure information”, including such various indexes as the systolic blood pressure value, diastolic blood pressure value, average blood pressure value, pulse wave, pulse beat, artery hardness, and so on.
Generally speaking, a blood pressure information measurement device cuff (called simply a “cuff” hereinafter) is used in the measurement of blood pressure information. Here, “cuff” refers to a band-shaped or ring-shaped structure that includes a fluid bladder having an inner cavity and that can be wrapped around part of a body, and that is used to measure blood pressure information by injecting a fluid such as air, a liquid, or the like into the inner cavity and inflating or deflating the fluid bladder. In particular, cuffs that are used by being wrapped around the arm are sometimes called “manchettes”.
Normally, an air bladder, formed in a bladder shape by layering comparatively flexible sheet-shaped members configured of a resin or the like and connecting the edges thereof, is used as the fluid bladder contained within the cuff. Because this air bladder is configured of a comparatively flexible member as mentioned here, there is a tendency for wrinkles to appear with ease in the surface of the air bladder when the cuff is wrapped around the measurement area.
The appearance of wrinkles in the air bladder causes the skin to be pinched by the wrinkles and blood stasis to occur, sudden pressure fluctuations to occur due to the wrinkles suddenly disappearing or receding when the air bladder is being inflated/deflated, and so on, and the precision with which the blood pressure information is measured to be negatively influenced. Furthermore, the appearance of a deep wrinkle in the air bladder causes the fitting area of the cuff to be unevenly pressurized, the wrinkle to interfere with the flow of air within the air bladder, and the artery to not be sufficiently pressurized, and so on. Further still, because there are individual variations in the fitting area for the cuff, wrinkles will appear with varying frequency due to such differences in the shape of the fitting area (primarily differences in the circumferential length, differences in the curvature factor, and so on); the appearance of wrinkles will then result in variations in the measurement precision.
A cuff configured so as to include two or more air bladders has been proposed for the purpose of more precisely measuring a pulse wave and obtaining an index or the like indicating a blood pressure value, artery hardness, or the like. JP-2000-79101A (Patent Citation 1), JP-2005-185295A (Patent Citation 2), JP-2007-44362A (Patent Citation 3), JP-2008-307181A (Patent Citation 4), and so on are known as literature disclosing a cuff configured so as to include two or more air bladders.
With a cuff that includes two air bladders as disclosed in these pieces of literature, the configuration that is mainly employed has a low-capacity air bladder used for pulse wave measurement being covered by a high-capacity air bladder used to block the blood in order to measure a pulse wave with a high level of precision. Wrinkles appearing in the low-capacity air bladder used for pulse wave measurement may occur in a cuff having such a configuration. The wrinkles that appear in the surface of the low-capacity air bladder will have an extremely high degree of influence on the blood pressure information measurement precision as described above, meaning that the original purpose of measuring a pulse wave at a higher level of precision will not be achieved. Therefore, when employing a cuff having such a configuration, it is absolutely necessary to make improvements for effectively suppressing the appearance of wrinkles in the surface of the low-capacity air bladder used for pulse wave measurement.
Meanwhile, JP-2006-81667A (Patent Citation 5), JP-2006-81668A (Patent Citation 6), JP-2008-99944A (Patent Citation 7), and so on can be given as examples of literature disclosing a cuff configured so as to be capable of suppressing the appearance of wrinkles in an air bladder.
With the cuff disclosed in the stated JP-2006-81667A, the configuration is such that a band-shaped member extending along the direction in which the cuff is wrapped is disposed within the air bladder, and the appearance of wrinkles is suppressed by forming an air flow channel along both sides of the band-shaped member in the width direction thereof.
Meanwhile, with the cuff disclosed in the stated JP-2006-81668A, the configuration is such that a breathable member configured of a sponge or the like is disposed within the air bladder, and the appearance of wrinkles is suppressed by securing air flow channels within the air bladder using the air passages that are formed within the breathable member.
Furthermore, with the cuff disclosed in the stated JP-2008-99944A, the configuration is such that a sliding sheet serving as a low-friction member is disposed between an outer cover that encloses the air bladder and the surface of the air bladder that pressurizes the body, and the appearance of wrinkles is suppressed by making it easier for the air bladder to slide upon the sliding sheet.    Patent Citation 1: JP-2000-79101A    Patent Citation 2: JP-2005-185295A    Patent Citation 3: JP-2007-44362A    Patent Citation 4: JP-2008-307181A    Patent Citation 5: JP-2006-81667A    Patent Citation 6: P-2006-81668A    Patent Citation 7: JP-2008-99944A